Compact full frame illumination and imaging system for a photocopier

Abstract

A compact, full-frame flash illumination system is disclosed. In a unity mode of operation, a lens, mounted within a light housing, projects an image of a document onto a photoreceptor belt. In a reduction mode of operation, the lens is translated towards the photoreceptor along a non-linear path which maintains document registration at the image plane. Simultaneously, the platen is translated upward by a mechanical drive arrangement to maintain conjugate requirements.

What is claimed is: 
     
       1. A compact, flash illumination and imaging optical system for a photocopier comprising in combination: a platen member for supporting original documents to be copied;   an enclosed illumination housing positioned beneath said platen member, said housing having diffuse, highly reflective interior surfaces;   a flash illumination means within said illumination housing adapted for periodically providing a generally uniform level of illumination at said platen surface,   a wide angle, relative-illumination compensated lens movably mounted in the floor of said housing for projecting document images along an unfolded optical path onto a photosensitive image plane; and   means for changing the magnification of said optical system, said means including a first means for changing the platen-to-image plane conjugate and a second means for translating said lens along a non-linear path towards and away from said image plane to project the document image onto the image plane at the desired magnification while maintaining document registration.   
     
     
       2. The optical system of claim 1 wherein said first means includes means for vertically translating said platen. 
     
     
       3. The optical system of claim 2 wherein said platen member comprises a generally rectangular frame member having an aperture thereon which seats the document platen, said frame member having downwardly extending side surfaces which maintain a sliding, light-tight contact with adjacent, stationary housing walls during said platen translation. 
     
     
       4. The optical system of claim 3 wherein said frame member further includes a plurality of cam follower members mounted along the edges of said frame member and wherein said vertical platen translation means includes a plurality of shaft members having mounted at the ends thereof a plurality of cam members, said shaft members mounted along the exterior surface of said housing so as to position said cam members in operative relationship with said cam follower member. 
     
     
       5. The optical system of claim 4 wherein said platen translation means further includes means to rotate said shafts for a period of time associated with a selected system magnification change, whereby said cam members operate against said cam follower member to vertically translate said platen member to a position which compensates for object-to-image conjugate changes introduced by said magnification change. 
     
     
       6. The optical system of claim 1 wherein the area enclosed by said housing varies as a function of the particular magnification. 
     
     
       7. A flash illumination and imaging optical system for an electrophotographic reproduction device, comprising, in combination, a transparent platen member for supporting original documents to be reproduced,   an illumination housing in optical communication with said platen member, said housing containing a flash illumination means adapted to periodically provide a generally uniform level of illumination at said platen surface,   a projection lens movably mounted in said housing for projecting document images along an unfolded optical path onto a photosensitive image plane, and   means for changing the magnification of said optical system, said magnification changing means including a first means for changing the platen-to-image plane conjugate and a second means for translating said lens along a non-linear path towards and away from said image plane so that said lens projects the document image onto the image plane at the selected magnification while maintaining document registration.   
     
     
       8. The optical system of claim 7 wherein said housing interior walls present a diffusely reflective surface to said flash illumination. 
     
     
       9. The optical system of claim 7 wherein said lens is a wide angle, relative illumination, compensated lens. 
     
     
       10. The optical system of claim 7 wherein the area enclosed by said housing varies as a function of the particular magnification. 
     
     
       11. The optical system of claim 1 wherein said first means includes means for vertically translating said platen.